Drain plugs are commonly used for sealing fluid drain holes, such as those found in vehicle engine oil pans and the like. Because of the large number of different vehicle manufacturers, it is common for vehicle maintenance shops to keep a supply of many different wrenches on hand, in both metric and English units, for removing and reinstalling different drain plugs. Because oil pan drain plugs are typically accessed from a pit in the floor below the vehicle, it is often necessary for the maintenance facility to keep many different sizes of wrenches within easy reach of a service technician located in the pit, which is typically dark, dirty, and cramped. However, it is generally undesirable to use adjustable wrenches (e.g., crescent wrenches), since those tend to round off the corners of the drain plug heads, rendering them unusable.